There are at present no evidence-based interventions for marijuana use during pregnancy, despite its being by far the most commonly used illicit drug during pregnancy (particularly among African-American women), and despite growing evidence that it may have a range of long-term cognitive and neurobehavioral consequences (e.g., Day, Leech, and Goldschmidt, 2011; Minnes, Lang, and Singer, 2011; Willford, Chandler, Goldschmidt, and Day, 2010). Further, as with other substances of abuse, the majority of persons needing treatment for marijuana use disorder neither receive nor want it (SAMHSA, 2012). Universal screening and brief intervention in primary care settings, which has shown significant promise with alcohol and tobacco use, has thus been recommended for further investigation with respect to marijuana use in pregnancy (Minnes, et al., 2011). However, implementation of brief interventions in medical settings has been limited by a range of substantial obstacles such as lack of time and willingness among providers, and difficulty maintaining adherence to key brief intervention principles. In contrast, technology-delivered brief interventions can be completed during normal wait times without staff involvement, are perfectly replicable, facilitate disclosure, and are relatively inexpensive to deploy. They have therefore received considerable attention as a possible way to address unhealthy substance use in primary care settings, with promising evidence of their efficacy in systematic reviews (Riper, et al., 2009), as well as in trials specifically with pregnant and post-partum women (Ondersma, et al., 2012; Ondersma, Svikis, and Schuster, 2007; Ondersma, Svikis, Thacker, Beatty, and Lockhart, 2013). This R34 clinical trial planning grant therefore proposes the development and preliminary validation of two high- reach and mutually compatible technology-based interventions for marijuana use during pregnancy. The first, a theory-based, synchronous, and highly interactive computer-delivered brief intervention, will be based on an emerging knowledge base regarding key elements of efficacious technology-delivered interventions. The second intervention, a series of tailored text messages, will build on the rich literature regardin key tailoring elements. These interventions will be developed and refined with input from pregnant women who report active use of marijuana, as well as from health care providers. They will subsequently be tested-alone and in combination-in a pilot randomized trial involving 80 women actively using marijuana during pregnancy. This Stage IA and IB pilot work would set the stage for a confirmatory Stage II trial. It would also produce the first high-reach brief interventions for marijuana use during pregnancy. If effective, these approaches could have a substantial population impact on marijuana use among pregnant women, with potential for lifelong improved outcomes for both mother and child.